An internal combustion engine having a supercharger (exhaust-type supercharger with variable nozzle) is conventionally known. This supercharger includes a turbine, a variable nozzle and a compressor. This turbine is provided on an exhaust gas passage of the internal combustion engine and driven by energy of the exhaust gas. The variable nozzle can change an opening-area of an approach zone through which the exhaust gas entered into the turbine. The compressor is provided on an intake air passage of the internal combustion engine and driven when the turbine is driven. A bypass passage and a control valve are furthermore provided to the exhaust gas passage of this internal combustion engine. The bypass passage is a branched passage from the exhaust gas passage and by-passes the turbine. The control valve is provided on the bypass passage and can change an opening-area of the bypass passage. The internal combustion engine is hereinafter simply referred to as “engine.”
The compressor noted above compresses air flew into the compressor and discharges the compressed air so as to be entered into a combustion chamber of the engine. That is, a supercharging is performed. More specifically, the supercharger adjusts the opening-area of the bypass passage by controlling the control valve based on operating condition of the engine and changes the opening-area of the approach zone by controlling the variable nozzle based on the operating condition of the engine. The amount of the energy of the exhaust gas entered into the turbine (hereinafter referred to as “energy entered into the turbine”) is controlled by the control valve and the variable nozzle. Pressure of air entered into the combustion chamber of the engine (supercharging pressure) is thereby matched to a value appropriate to the operating condition of the engine.
One of the conventional control devices provided for the internal combustion engines (hereinafter referred to as “conventional device”) controls the energy entered into the turbine by adjusting the control valve and the variable nozzle based on engine rotation speed. The conventional device thereby controls the supercharging pressure (for example, see JP2005-146906A).